1. Field of the Invention
This invention relates to a connector for connecting structural members and more particularly to a connector for connecting structural members for a wooden building, which include a beam, a column etc.
2. Discussion of the Background
Reinforced concrete (RC) buildings are of an integral construction, but wooden buildings are constructed by connecting many structural members, including for example a column and a beam.
In wooden buildings, therefore, the strengh of the structural members is important, but the strengh of connenctors for the structural members is also very important.
There are many types of prior art connectors.
One connector comprises a bolt and nut assembly.
Another connector further comprises a metal plate, which is patched to two members and which transmits an axial force, a shear force or bending moment generated in one member to the other member.
However, long span wooden buildings are constructed using timbers having a large sectional area cosisting of bonded wood.
These timbers can bear higher loads than the standard timbers because of their large section.
Therefore, a connector for connecting these timbers requires higher corresponding connection strength.
Now, by patching the metal plate to these timbers and clamping the metal plate and the timbers with bolts or nails, a predetermined connecting strength can be acquired.
However, connecting structures using bolts or nails have the following problems.
First of all, in case of nails, to acquire a large connecting strength a large area for nailing is required in the connecting surface of the timbers because the corresponding number of nails must be nailed with a predetermined pitch so as to prevent fracturing of the timbers.
Therefore, connectors with nails cannot attain much connecting strength.
Secondly, in case of bolts, a large connection strength can be acquired, but a large deformation may be generated between timbers because there is a predetermined clearance between bolts and their corresponding holes.
Thirdly, applications of finishing materials are very difficult because the bolts which clamp the metal plates to the timbers, project beyond the surface of the metal plates.
Furthermore, metal plates require a predetermined size corresponding to the size of timbers so that architectural design may be impaired unless proper sizing exists.
The Japanese Utility Model Laid-Open No. 2-74403 discloses a connector for connecting a column and beam, comprising a base plate for supporting the beam, a plate member substantially perpendicular to the base plate, a mounting plate for mouting the connector to the column provided in one end of the plate member and a pair of rectangular protruded portions provided on two sides of the plate member, wherein the rectangular protruded portion defines a clearance between a surface of the rectangular protruded portion and an inner surface of a rectangular slot provided in the beam, said clearance being penetrated by a predetermined wedge.
Furthermore, the Japanese Utility Model Laid-Open No. 2-77204 discloses a connector for connecting two beams, comprising a base plate for supporting the beams, a plate member substantially perpendicular to the base plate and two pair of rectangular protruded portions provided on two sides of the plate member, wherein the rectangular protruded portion forms a clearance between a surface of said rectangular protruded portion and an inner surface of a rectangular slot provided in the beam, the clearance being penetrated by a predetermined wedge.
However, first of all, these connectors require the wedge essentially to connect a beam and column or two beams.
Secondly, the wedge must be fixed using a cover plate and bolts so as to prevent uplifting of the beam and thus the cover plate and bolts project beyond the top surface of the beam.
Therefore, the cover plate and bolts disturb the installation of flooring, especially when the flooring is aplied to the beam directly.
Thirdly, in the connection of the column and the beam, the connector is mounted to the column, the column is slightly inclined outwardly, the beam is lowered so that the rectangular protruded portion of the connector can be inserted into the rectangular slot of the beam and the wedge is driven into a clearance between an inner surface of the rectangular slot and an outer surface of the rectangular protruded portion so that the column is drawn into the beam.
Therefore, the column cannot be fixed before the connection of the beam and column is completed and thus the construction of a multi-layer building is very difficult.
Furthermore, the rectangular slot is more difficult to work than a round slot or hole.
Furthermore, the rectangular protruded portion and a corresponding portion of the beam are not integral so the rectangular slot causes a reduction of the sectional area of the beam, thus decreasing the connecting strength.